DR MARK LAMBERT Consultant in Anaesthesia RNTNE and UCL Hospitals

An Introduction to Anaesthesia 2019

So it’s 1am on your night shift…

•  You’ve had such a busy day….

•  Time to find a comfy place for a nap

But you can’t sleep…

•  Tax changes to the NHS pension scheme •  Crikey this makeshift bed is so uncomfortable

•  I really hope no horrible airway comes in tonight

Something is playing on your mind… What is it???

Airway

•  Because it all starts with ‘A’

•  Any hint of an “airway” problem means that anaesthetist gets called

•  Most airways are easy…

X

Here’s what I hope you might learn

•  Airway anatomy for anaesthetists

•  A basic framework for managing the airway in theatres

•  Think about easy and difficult airways

•  Some plans for failed airway management

Anatomy

The Glottis

Why do anaesthetists need to manage the airway?

•  Anaesthetic drugs –  Depress/abolish airway reflexes –  Cause relaxation of upper airway muscle tone –  Cause respiratory depression / apnoea

•  In an emergency –  Acute airway obstruction –  Failure to oxygenate/ventilate

Pharyngeal structures

A typical anaesthetic...

•  Andy, 32, has hurt his hip and needs it fixed •  You give your best anaesthetic

•  5 seconds later : he’s asleep •  15 seconds later : apnoea

•  What are you going to do next?

Intubate

Ventilate with facemask

Put in an LMA Fibreoptic laryngoscopy

Catch up on Love Island

Tracheostomy

Call for help

Have a quick coffee

Get out iPhone Ask your ODA/ODP/anaesthetic nurse to bail you out

Priority 1 :

Oxygenation

Preoxygenation

•  Minimal oxygen stores in the body

•  Functional residual capacity – 2500ml •  Oxygen demand – 250ml/min

•  Allows time before desaturation –  But rising CO2

Modern preoxygenation?

•  Optiflow/ THRIVE

–  High flow oxygen

–  Apneoic mass transfer of O2 to alveoli

–  Prolonged apnoea time without desaturation

Facemask ventilation

•  The most important anaesthetic skill ??? •  Harder than it looks •  One person / two person •  Adjuncts

•  Know where your facemask is •  Back up self inflating bag location

Facemask ventilation adjuncts

•  Oropharyngeal airway

•  Size : Incisor to angle of jaw (or ask your ODA)

Facemask ventilation adjuncts

•  Nasopharyngeal airway

•  Size : –  Women 6 –  Men 7

•  Use plenty of lube (and go carefully if you suspect basal skull fracture)

Back to Andy

•  He’s easy to facemask ventilate

•  Will we hold a mask on his face for the entire case?

•  Other airway options include –  Laryngeal mask airway –  Endotracheal tube

Laryngeal mask airway (LMA)

•  Blind insertion •  Cuff to improve seal •  Hands free •  Sits above the glottis

•  Variety of second generation devices available but all work on a similar principle

Second generation SADs (LMAs)

•  .

LMA position

•  Like a facemask over the larynx

•  Doesn’t protect against aspiration of gastric contents

•  May be helpful in difficult facemask ventilation

Endotracheal tube

•  “A secure airway is a cuffed tube in the trachea” –  Allows ventilation –  Protects against aspiration

•  Normally placed under direct vision (laryngoscopy)

Direct Laryngoscopy

•  Uses a metal blade with a light source to create a direct line of sight to the glottis

•  Can be stressful (for you and the patient)

•  Laryngoscopes come in a variety of shapes and sizes

Video-laryngoscopy

•  Uses a camera and screen to allow visualisation of the glottis without direct line of sight

*But you still have to get the tube in!!!

Fibre-optic Laryngoscopy

•  Fibreoptic scope used to provide an indirect view of the glottis/trachea

•  Scope then used as a guide to pass ETT into trachea

The view from a laryngoscope

The Glottis

Recognising when airway management is going to be difficult

•  History –  Previous anaesthetic problems / difficult airway alert –  Congenital disorders associated with difficult airway (Anatomy) –  Co-morbid conditions (Pathology)

•  Examination –  General appearance –  Specific tests

•  Special investigations –  Rarely used (nasal endoscopy/CT)

Specific ‘airway’ tests

•  Mallampati

•  Mouth opening

•  Neck movement –  Thyromental distance

•  Jaw protrusion

Oral / tracheal axis

Sometimes it’s obvious

But….

•  Tests are notoriously unreliable and focus on difficult intubation

•  Difficult facemask ventilation is more worrying than difficult intubation –  Beards / big neck / high BMI / Elderly

•  Trust your instincts! –  Ask for senior advice or help early

Planning for failure

•  Always have a plan B for managing the airway (and communicate this to the rest of the team) –  If not possible to place an endotracheal tube what next?

•  Plan B – LMA (and call for help) •  Plan C – Facemask ventilation (+/- Guedel) (+/- wake up) •  Plan D – Emergency cricothyroid puncture

•  Guidelines exist to help plan for the unexpected but it’s much easier if you’ve identified trouble beforehand

Extubation

•  Taking the airway device out can be as risky as putting the device in

•  Increasing recognition of this –  Improved training / support –  Guidelines (Difficult airway society)

•  If you had difficulties at intubation then extubation also likely to be troublesome…

Key Points

•  Always think ‘oxygenation’

•  Consider whether mask ventilation or intubation (or both) will be a problem –  Trust your instincts –  Ask for help early

•  Have a back-up plan ready and make sure everyone else knows what it is

Here’s what I hope we did…

•  Airway anatomy for anaesthetists

•  A basic framework for managing the airway in theatres

•  Think about easy and difficult airways

•  Some plans for failed airway management

Please ask your questions now….

Thanks!